• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2002년도 생물공학의 동향 (X)
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• pp.419-422
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• 2002

Fermentative hydrogen production by Citrobacter sp. Y 19 was investigated in batch culture. Optimal hydrogen production activity was observed at pH 6 - 7 and temperature of $36^{\circ}C$, and hydrogen yield and maximal hydrogen production rate were 1.12 mmol/mmol glucose and 32.3 mmol/g cell${\cdot}$h, respectively. With glucose as a substrate, the bacterium produced ethanol, acetate, and carbon dioxide as major glucose fermentation by-products. Y19 could utilize various sugars such as galactose, fructose, lactose, sucrose, and starch for cell growth and hydrogen production.

• Journal of Microbiology and Biotechnology
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• 제23권12호
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• pp.1673-1682
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• 2013

Citrobacter sp. is a cause of significant opportunistic nosocomial infection and is frequently found in human and animal feces, soil, and sewage water, and even in industrial waste or putrefaction. Biofilm formation is an important virulence trait of Citrobacter sp. pathogens but the process and characteristics of this formation are unclear. Therefore, we employed in vitro assays to study the nutritional and environmental parameters that might influence biofilm formation of C. werkmanii BF-6 using 96-well microtiter plates. In addition, we detected the relative transcript levels of biofilm formation genes by RT-PCR. Our results indicated that the capacity of C. werkmanii BF-6 to form biofilms was affected by culture temperature, media, time, pH, and the osmotic agents glucose, sucrose, NaCl, and KCl. Confocal laser scanning microscopy results illustrated that the structure of biofilms and extracellular polysaccharide was influenced by 100 mM NaCl or 100 mM KCl. In addition, nine biofilm formation genes (bsmA, bssR, bssS, csgD, csgE, csgF, mrkA, mrkB, and mrkE) were found to contribute to planktonic and biofilm growth. Our data suggest that biofilm formation by C. werkmanii BF-6 is affected by nutritional and environmental factors, which could pave the way to the prevention and elimination of biofilm formation using proper strategies.

• Journal of Microbiology and Biotechnology
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• 제13권5호
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• pp.717-724
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• 2003

A newly isolated Citrobacter sp. Y19 catalyzes the CO-dependent $H_2$ production (biological water-gas shift reaction) by the actions of CO dehydrogenase (CODH) and hydrogenase. Y 19 requires $O_2$ for fast growth, but its $H_2$ production activity is significantly inhibited by $O_2$. In the present study, the effect of $O_2$ on the activities of CODH ard hydrogenase was investigated quantitatively in both whole cells and broken cells, based on CO-dependent or methyl viologen (MV)-dependent $H_2$ production in addition to CO-dependent MV reduction. In crude cell extracts, CODH activity was mostly found in the soluble fraction. Inactivation of CODH and hydrogenase activities by $O_2$ followed the first-order decay kinetics, and the dependence of the rate constants on $O_2$ partial pressure could be expressed by the Michaelis-Menten equation. In whole cells, the maximum deactivation rate constants ($k_{d,max}$ of hydrogenase and CODH were quite similar: $0.07{\pm}0.03 min^{-1}\;and\;0.10{\pm}0.04 min^{-1}$, respectively. However, the first-order rate constant ($k_{d,max}/K_s$) of CODH ($0.25\;min^{-1}\;atm^{-1}$) at low $O_2$ partial pressures was about 3-fold higher than that of the hydrogenase, since the half-saturation constant ($K_s$) of CODH was about half of that of hydrogenase. In broken cells, both enzymes became significantly more sensitive to $O_2$ compared to the unbroken cells, while $k_{d,max}/K_s$ increased 37-fold for hydrogenase and 6.7-fold for CODH. When whole cells were incubated under anaerobic conditions after being exposed to air for 1 h, hydrogenase activity was recovered more than 90% in 2 h suggesting that the deactivation of hydrogenase by $O_2$ was reversible. On the contrary, CODH activity was not recovered once deactivated by $O_2$ and the only way to recover the activity was to synthesize new CODH. This study indicates that $O_2$ sensitivity of $H_2$ production activity of Citrobacter sp. Y19 is an important drawback as in other $H_2-producing$ bactria.

• Journal of Microbiology
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• 제42권2호
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• pp.139-142
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• 2004

To identify genes involved in the decolorization of brilliant green, we isolated random mutants generated by transposon insertion in brilliant green-decolorizing bacterium, Citrobacter sp. The resulting mutant bank yielded 19 mutants with a complete defect in terms of the brilliant green color removing ability. Southern hybridization with a Tn5 fragment as a probe showed a single hybridized band in 7 mutants and these mutants appeared to have insertions at different sites of the chromosome. Tn5-inserted genes were isolated and the DNA sequence flanking Tn5 was determined. By comparing these with a sequence database, putative protein products encoded by bg genes were identified as follows: bg 3 as a LysR-type regulatory protein; bg 11 as a MalG protein in the maltose transport system; bg 14 as an oxidoreductase; and bg 17 as an ABC transporter. The sequences deduced from the three bg genes, bg 2, bg 7 and bg 16, showed no significant similarity to any protein with a known function, suggesting that these three bg genes may encode unidentified proteins responsible for the decolorization of brilliant green.

• 미생물학회지
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• 제33권2호
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• pp.92-96
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• 1997

Pseudomonas sp. strain DJ77로부터 클로닝한 catechol 분해와 관련된 phnDEFG 유전자들이 존재하는 pHENX7에서 phnF 유전자의 염기서열을 밝혔다. Extradiol dioxygenase 유전자인 phnE와, 2-hydroxymuconic semialdehyde dehydrogenase를 생산하는 phnG 유전자 사이에 존재하는 유전자 phnF는 432 bps로 된 하나의 open reading frame(ORF)으로 존재하였고, 여기서 유추한 아미노산은 143개로 분자량 13,859 dalton의 polypeptide를 만들어 내고 있다. phnF 유전자는 Sphingomonas sp. strain HV3 catE 유전자 부위와 sphingomonas yanoikuyae B1의 xylE와 xylG 사이에 존재하는 ORF 부위의 염기서열과 각각 99%, 68.6%의 상동성을 가지고 있었다. 또한 PhnF 단백질의 아미노산서열은 citrobacter freundii DSM30040의 orfY 부위의 아미노산서열과 62.3%의 상동성이 있었다.

• 한국식품영양학회지
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• 제9권1호
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• pp.29-36
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• 1996

Naengmyon is a Korean buckwheat noodle with chilld broth, and the juice of dongchimi, a Korean radish pickle fermented with wild lactic acid bacteria, has been used as the broth for naengmyon traditionally. The purpose of this study was to demonstrate the inhibitory effect of dongchimi-juice against coliform bacteria in model system of naengmyon-broth. Dongchimi-juice was made from radish juice by the cultivation of lactic acid bacteria which had been isolated from kimchi. Three types of naengmyon-broth, beef-broth type, dongchimi-juice type and the mixed type, were made as model systems, and then the changes in viable cell counts of seven coliform bacteria, Klebsiella planticola Bo2, X. terrigena CO8, K. pneumoniae DOI, K. ozaenae DO4, Enterobacter sp. AO2, Enterobacter sp. CO7, Citrobacter sp. BO7 and Escherichia sp. DO3, which had been added to each type of naengmyon-broth in advance, were investigated during storage at 3$0^{\circ}C$ All coliforms grew rapidly in naengmyon-broth of beef-broth type, while none grew in dongchimi-juice type or in the mixed type. All coliforms died out far more rapidly in dongchimi-juice type than in mixed type. The decreasing slopes of Citrobacter sp. Bo7, K. planticola BO2, X. terrigena CO8 and K. ozaenae DO4 were more steep than those of the rest. It was thought that the preparation method of Korean traditional naengmyon such as dongchimi-naengmyon or Pyongyang style-naengmyon, which uses oxy dongchimi-) juice or the mixture of dongchimi-juice and beef-broth, would be very effective for preventing the growth of coliform bacteria from naengmyon.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XII)
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• pp.412-413
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• 2003

• Toxicological Research
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• 제23권1호
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• pp.65-72
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• 2007

This study was conducted to obtain information of the oral dose acute toxicity of PGB-2, a novel polyglucosamine polymer produced from Citrobacter sp. BL-4 (a new strain) in male and female mice. Mortality, body weight changes, clinical signs were monitored during 14 days after single oral dose of test article at dose levels of 2000, 1000, 500, 250 and 125 ml/kg. Gross lesions, organ weight and histopathology of principal organs were examined after necropsy. As the results, we could not find any mortalities, clinical signs, changes in the body weight and gross findings except for white foci in the liver. In addition, no PGB-2-treatment related abnormal changes on the organ weight and histopathology of principle organs were detected except for atypical signs of liver. White liver foci were confirmed as focal infiltration of inflammatory cells. The results suggest that the PGB-2 is relatively safe in mice but the possibility of hepatotoxicity could not be excluded. The $LD_{50}$ and approximate LD in mice after single oral dose of PGB-2 were considered over 2000 mg/kg, respectively. In future, the potential hepatotoxicity of PGB-2 should be evaluated through the repeat dose toxicity test prior to develop as a new agent.

• 한국어병학회지
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• 제36권2호
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• pp.239-250
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• 2023

최근 뱀장어 (Anguilla japonica)에서 발생하고 있는 질병을 파악하기 위하여 질병 모니터링을 실시하였다. 2021년 5월부터 2022년 3월까지는 폐사가 발생한 7개의 양만장 유래의 뱀장어를 7회 검사하였다. 모든 양만장에서 JEECV가 검출되었고 양만장마다 1-2종의 세균 (Edwardsiella anguillarum, E. piscisida, Aeromonas sp., Citrobacter freundii, Lactococcus garviae 혹은 Vibrio sp.)이 복합감염이 일어나 있었다. 2022년 3월부터 2023년 10월까지는 전라남도 영광의 한 양식장에서 매달 정기적으로 총 22회 검사를 실시하였다. JEECV가 22회 검사 중 10회 검출되었고 폐사가 발생하지 않는 시기에도 꾸준히 검출되었다. 세균으로는 E. anguillarum, C. freundii, Aeromonas sp.와 Vibrio sp가검출되었으나 E. anguillarum이 분리된 개체만이 간의 농양과 출혈 병소가 일관되게 관찰되었고 다른 세균은 임상증상이 없는 경우가 많았다. 모니터링의 결과를 종합하면 양만장에서의 폐사는 JEECV 단독감염보다는 JEECV가 세균과 복합감염일 경우에 발생하였다. 그러므로 뱀장어의 폐사를 줄이기 위해서는 JEECV와 E. anguillarum의 관리에 중점을 두고 복합감염을 줄이는 것이 중요한 것으로 생각된다.

• 한국생명과학회:학술대회논문집
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• 한국생명과학회 2005년도 국제학술심포지움 The 44th Annual Meeting of Korean Society for Life Science
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• pp.127-127
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• 2005